I'm sure everyone has felt and keeps on feeling the frustration of peforming very well in a ranked game, but yet of losing the game because of less performant players or afk players or trolls alike. Riot introduced the Champions Mastery system, that, along with the mastery in game banners, came with a peformance evaluation ranging from D to S (with + and - as well) displayed in the post-game lobby.
**My suggestion is quite simple: on top of the actual algorithm to calculate how many LP one gains/loses after winning/losing a game, why not scale the resulting number by one's performance indicator (which I talked about right above)?**
To make a few quick examples, let's say my team loses the game but I score an S, my LP change would be -20, let's make it a -10; at the contrary, let's say I performed quite bad (e.g. C) but got carried to victory by my good team, I would win 20, let's make it 15 (these are just example numbers). Of course I'm not saying to not lose LP when someone loses a game. The same way, we could also consider the presence of one or more AFK players (or disconnected) to soften the LP loss, after all it's not my fault if I'm playing 3 v 5, but yet I'm losing a nice chunk of my LP.
Before going on I'd like it to be clear that the concept of this suggestion is based on a performance indicator, and Riot's mastery grades gave me the idea. The ideal indicator should obviously be fair and balanced and should reward players who actually contribute to victory, in all the many ways and forms; I don't know if the mastery grades are like that, but for the sake of my suggestion let's consider such an ideal indicator.
Since I've already presented this suggestion and answered to some skeptics, I'll try to point out a few important things.
* Some were afraid this system might push players towards safer, conditioned playstyles in order to achieve a better KDA or anyway provide them with a choice between score and teamwork.
I don't think this would be an actual problem. The primary goal is still to win, thus the most logic choice is about what to do to win the game, having a good score should serve this primary goal. It wouldn't be smart to play exclusively for your own good score, if it means neglecting the team and eventually losing the game, because you would lose LP this way. You might instead gladly sacrifice your score in order to win the game and LP. This is how I see it at least.
* Someone presented to me the case in which a player would score a very high number of deaths, mostly sacrificing himself to help the team win the fights and eventually the game, thinking it wouldn't be fair for him to win less LP because of his bad score.
To die many times means a very bad performance, you gave a lot of advantage to your opponents. If you died all those times as a sacrifice and your team managed to win the game, there you have your reward, you win LP and you advance in the ranking, your many deaths were not in vain afterall, but it's obvious that you could have done better for your team dying less times. If your team doens't win, then it's clear you definitely helped them losing.
* Another one presented a similar scenario in which a support Blitzcrank scores quite bad, dying a lot of times, but does a super hook that basically solves the game alone and lets the team win right after.
Same story, he played bad, it's most likely that the rest of his team did a great job holding up on the disadvantage he provided. His good play is rewarded with him winning LP, why less than normal? Because it's kinda obvious that his team would have had less problems winning that game if he didn't play so bad during the game. A single play doesn't carry a game, especially if it comes from an overall bad performance.
* "You play top and go 1/0 in laning phase. Then their mid LB who is fed ganks you and from there on you proceed to loose lane because you are playing against a snowball champion. You play top and go 1/0 in laning phase. Then their mid LB who is fed ganks you, but don't loose lane because you are playing against AD Soraka top. Why should the first game lose you more LP than the second one?"
I'd say the second game should lose you less LP because you won your lane (vs that questionable AD Soraka, who will probably win less LP than her teammates) and the goal of ranked play is also to try placing each player in the division they belong to. This is actually a very extreme case which can be compared to finding a troll or an intentional feeder in your lane: why should I earn more LP if I got my good score given for free? The problem is bigger here and wouldn't be about the LP adjustment. Why would I deserve to win and gain LP if they just lost intentionally? It's a problem not even the actual system solves, at all, but it's also an outlier problem that is considered to be out of the norm, to be clear, there are bans for these cases.
In conclusion, not only this would seem a much more fair way to assign LP for ranked games, but it could also have a lot of benficial effects on the community! It could partially take away the feeling of having LP drained by your bad teammates, but mostly it would be a stronger incentive for any player to play at his best under any circumstances (because you can retain some LP if you're losing but you played well) and it could also help players to focus more on their own mistakes than on their teammates' ones, hopefully resulting in less toxicity. (As a more technical note, I think it would also reduce the variance around a player's expected rank tier-division, thus increasing accuracy and reduce the settling time needed to reach it, overall making the system more efficient).
Sorry for the long text, I hope you will take the time to read my post as I truly believe in this suggestion and of course invite you to comment with your opinions about it. Thanks.